Aforesaid turbine blades have been known for a long time from the prior art. As a rule, they have a blade airfoil which is traversed by cavities which are separated from each other by means of ribs. The ribs extend from the suction-side wall to the pressure-side wall and along the longitudinal direction of the blade airfoil, i.e. from the platform to the blade tip. Cast turbine blades in this case have a transition region between blade airfoil and platform surface which, by means of a fillet-like rounding, thickens the blade sidewalls, i.e. the suction-side wall and the pressure-side wall, in this region. In the transition region, therefore, there is a material accumulation which also brings with it a sudden change of rigidity of the blade airfoil. The blade airfoil is therefore stiffer on the platform side than in its middle region or on the blade-tip side. On account of this sudden change of rigidity, larger temperature gradients can occur during In order to avoid secondary damage in the gas turbine, in which such a turbine blade is installed and used during operation, as a result of fragments which become detached from the turbine blade, the turbine blade is exchanged after achieving a predetermined maximum service life.
From the prior art it is known, moreover, to at least partially extend the service life by a thicker thermal barrier coating being applied in the regions of sudden changes of rigidity than in the regions without such material accumulations. As a result, the temperature gradients can be reduced.
In addition, a gas turbine blade, the leading edge of which, exposable to inflow by a hot gas, is impingement cooled, is known from EP 1 420 142 A1. The impingement cooling openings which are required for this purpose are arranged in a rib which supports the blade airfoil between suction-side and pressure-side walls. In this case, the impingement cooling openings for the most part are distributed uniformly over the height of the blade airfoil and invariably arranged in the middle between pressure side and suction side in order to ensure uniform cooling of the leading edge.